OBJECTIVES: a. The overall objectives of this project are to study the interaction of vitamin B12 with a variety of binding proteins in order to elucidate the basic mechanisms of B12 absorption, transport, and storage in health and disease. b. This year our goals were to: 1) Complete the purification of the intrinsic factor receptor from the guinea pig ileum using affinity chromatography. 2) Develop the affinity columns of B12 covalently coupled to Sepharose and purify the B12 binding proteins, intrinsic factor, transcobalamins I and II. 3) Develop a solid phase radioassay procedure to investigate the mechanism for the release of B12 from intrinsic factor.